This observation is consistent with a mirror phenotype consisting in macrocephaly in individuals with duplications encompassing AKT3 and segmental hypertrophy (in the form of hemimegalencephaly or syndromic megalencephaly) in individuals with missense mutations leading to increased mTOR signaling that are usually—but not always—limited to mosaic brain tissues (Fig. 2a) (Conti et al. 2015; Lee et al. 2012; Poduri et al. 2012; Riviere et al. 2012; Wang et al. 2013; Nellist et al. 2015; Takagi et al. 2017). This evidence concerns the gene AKT3 and hemimegalencephaly.